Piston



A. FLOWER Juy l935.,

PISTON File March 7, 19.55

` UNITED sTATEs PATENT OFFICE PISTON Alpheus Flower,

London, England Application March 7, 1933, Serial No. 659,970r In Great Britain March 9, 1932 11 Claims.

This invention relates to multi-piece pistons for fluid-pressure engines; and particularly to the bi-metallic kind comprising a crown or head formed of aluminium vor other light alloy, preferably as a casting, with integral wrist-pin or gudgeon-pin bosses or other body parts to. which is attached a tubular skirt of cast iron, steel, or some other good wear-resisting material.

The main object of the present invention is the provision of an improved method of and means for attaching the skirt vto the head or some other piece of the piston Vwhereby said means constitute `a device for compensating for the varying expansion and contraction of the differentrmetals. A further object is to provide an improvedarrangement with which the cost of production will be reduced, particularly inasmuch as it allows of `the head being cast independently of the tubular skirt and subsequently securely united to it in an inexpensive and simple manner.

Furthermore, in the usual type of cast-in bi-metallic-pistons `the. contraction of the aluminium from its hot state, after the casting operation, provides a clearance between thetwo bosses for the wrist-pins, etc., inside the skirt; and where thel skirt lmeets the head or lower portionV of the ring belt of the piston, or at the lower end of the skirt, the initial contraction clearance is too great and allows the head or other' parts to move relatively to the steel skirt. A further object of thisinvention is to obviate this disadvantage. Y

A piston, according to the main feature of the invention, has a tubular skirt'provided peripherally with a substantially flat disc or annular lportion through which the skirt is attached to another piece of the piston. Y

According to a further feature of the invention, the inner periphery of the annular .portion is surrounded by a iiange which extends inwardly of the skirt and, engages the otherpiece of the pistongfor attachment purposes. This flange may be frustum-shaped, with or without an outwardly-iiared edge, or with or without a keying hole. v

According to a still further feature, the steel skirt-has a portion, preferably at the top or bottom thereof, originally enlarged in diameter externally, and after the metal of the head or other part of the piston has been cast and has cooledfoff the skirt is drawn through a ring. of the desired nal dimension of the skirt, or treat- 1:iis

ed in an equivalent manner, thereby bringing- 'vt-"55 the" enlarged portion back to Athe'proper dia-mmetals; that is, between the steel skirt andthe eter. By this means the clearance between the exterior wall of the head or other part of the cast metal and the inner wall of the steel skirt can be reduced, thereby preventing any independent rocking of one part relatively to the other. 5

Figure l is a verti-cal section through the wristpin or gudgeon-pin axis of one form of lai-metallic piston according to the invention;

VFigure 2 is a cross-section on the line II-II 1D of Figure 1;

Figure 3 is a corresponding cross-section showing a modification;

Figure 4 is a vertical section through part of another. formof bi-metallic piston according `to theinvention;

Figure 5 is a fragmentary vertical section indicating another embodiment of the invention;

Figure 6 is a fragmentary vertical section, to a somewhat larger scale, indicating a stepV in the manufacture of the pistons shown in any of the foregoing figures; and v Figure 7 is `a similar View to that of'Figure 6, but it shows a modied arrangement.

Like numerals indicate like parts throughout V the figures. Y

In the constructions illustrated in Figures 1 to 4, showing a bi-metallic piston having a head 2 of aluminium alloy, formed integrally with body webs 3; 3 from which the wrist-pin or gudgeony pin bosses 4, 4 are supported, and a tubular skirt 5 of steel, the latter is provided peripherally, below where the wrist-pin will be, with a depression forming a substantially flat annular portion the centre of which is in the longitudinal plane of k the skirtthrough the wrist-pin axis.

In the arrangement of Figures 1 and 2, where there is a single flat annular portion 6 on each side, each of these has'ata its centre an aperture surrounded by a frustum-shaped lflange l, the

\ end o-f which, in the interior of the skirt, is outwardly-flared, as at 8, toprovide an increased keying eifect with the circular metal boss 9, beneath the wrist-pin bossesd, which is cast on to the flange 1.

Obviously the metal bosses 9 may be in the form of a belt lll extending wholly, or partly, as shown in Figure 3, around the piston, and there maybe two or more keying flanges 1 on each side of the piston, as is also indicated byV Figure 3. The cast 'metal inside the flanges maybe hammered into contact therewith after cooling'.

'This latter figure also shows a further method of securing the skirt through the annular portion 6 which may be Yused as' an alternative. to or `55 in conjunction with the arrangement of Figures 1 and 2. In Figure 3 the non-circular head of a bolt II is embedded in the belt IIJ co-axial with the flange 1, and the latter contains a nut I2 of similar outline and adapted, as by the provision of serrations I3, to be screwed tightly on to the bolt after the cast metal has cooled and shrunk. Tightening the nut forces the flange into contact with the surrounding metal. The nut can be locked by punching part of the bolt into the serrations I3.

In the arrangement of Figure 4 the head, as illustrated, is pre-cast and then bolted to the skirt at the flat annular portions 6 of the latter. Thus, the metal of the body of the head is also formed with a more or less similar depression I4 that will engage the inner face of the fiat annular portion 6 but be elsewhere spaced from the skirt, to allow of expansion of the head body. A bolt I5 with a fiat narrow head resting in the depressionand not extending as far outwardly as the main portion of the skirt is passed through the skirt land through a corresponding hole in the Abody `portion of the head. At its inner end there is a nut I6 which can be .tightened to lock the skirt and body portion securely together.

It is desirable to prevent relative rotation of the nut on the bolt, and for this purpose a disc washer II may be interposed between the nut and the adjacent inner face of the body portion, the washer being formed with outwardly-extend- `ing tangs I6, I8 of which one enters a hole I9 provided in the under-surface "of the wrist-pin boss '4 to prevent rotation of the washer, Whilst another tang can be bent up as shown to lock the nut after it has been tightened. In like man ner suitable holes 2U, 20 may be provided in the bolt `andin the body 'portion to receive a short stem or key 2| by which the bolt, when the nut is tightened, vwill be locked against rotation.

In a `preferredarrangement the bolt is formed with an enlarged shoulder 22 beneath its head (which is conveniently the portion of the bolt drilled to receive the bolt locking member 2|) and this enlarged shoulder ts the hole in the skirt and extends into a corresponding recess provided in the body portion, acting totake the shear load.

As stated, in practice at least twosuch attach- Inentmeanswould be provided for a piston, these being arranged diametrically opposite one another. To facilitate assembly, a longitudinal groove 23 is provided to receive the flat annular portion 6 and its internal flange 24, which springs into the hole in the head body.

In the modification of Figure 5, where the head is cast on tothe skirt, the flat annular portion 6 and the ilange 'I are co-axial with the wrist-pin bosses 4. This construction is somewhat lighter and cheaper to produce than that of Figures 1 and 2. The keying effect is increased by the provision of the holes 25.

4With a View to preventing relative movement between the head of the piston and the upper end of the skirt, these are preferably adapted in the mannerillustrated in Figure or Figure 7, where the clearances between the skirt and the cast metal are 'shown much exaggerated for the sake of clearness. There the skirt, prior to the casting operation, is not rof uniform bore; but at -its `upper and lower ends 26, 26 it isl enlarged slightly, as indicated in Figure 6 or '7.

In the arrangement of Figure 6, where the Vvskirtehds are enlarged both internally and ex- Vter-nally,it follows that ridges 21,21 are formed on the cast metal in the vicinity of the skirt enlargements during the casting operation. When, however, the metal has cooled, the skirt is drawn through a die, or treated in other ways, such that the enlarged portions 26, 26 at its upper and lower ends are brought into line with the remainder of its surface, as indicated in Figure 1, where the upper end of the skirt is shown in very close proximity to the ridge 21.

Consequently, in spite of the fact that the cast metal of the head may shrink from the skirt, leaving an initial clearance, when finally treated the clearance between the upper or lower end of the skirt and the cast metal can be reduced to any requisite amount, and by this means movement between the ends of the skirt and the cast metal can be entirely prevented.

The most inexpensive method of producing the skirt probably consists in the use of a skirt of uniform bore and thickness, of which the ends can then be enlarged to the necessary diameter, as described above, in connection with Figure 6. But an alternative method would consist in the use of a skirt of uniform bore and greater thickness at the two ends 26, 26 as shown in Figure '7, these thickened portions constituting the skirt enlargements referred to above and beinging ilattened, as by being drawn through a die, after the cast metal has cooled.

In all cases, after the enlargements have been attened, the clearances there should be such as to allow of Contact being made internally of the enlargements when the parts have expanded under the normal working temperatures.

It will be seen that by means of the invention a very rm and lasting attachment is evolved which compensates for the varying expansions of the two metals. The arrangement of Figure 4 lends itself to quick production; and furthermore this piston may be economically manufactured.

In all cases the disc or annular portion 6 of the depression in the skirt is sufliciently fiexibly connected to the rest oi' the skirt to move as the adjacent body portion of the head, which is secured to it, expands.

What I claim as my invention and desire to secure by Letters Patent of the United States 1s:-

1. A multi-piece piston having a head, a boss thereon, a tubular skirt, Vthis latter being provided peripherally on one of its non-thrust faces with a substantially flat circular portion through which the skirt is attached to the boss, -and a nut and bolt, each of which is locked vagainstturning, for eiecting said attachment.y

2. A piston, according to claim 1, where the head of the bolt lies against the outer face of the circular portion. Y

3. A multi-piece piston having a head, a b oss thereon, a tubular skirt,said skirt beingprovided peripherally on one of its non-thrust faces with a substantially at circular portion through which the skirt is attached to the boss, anda nut and bolt,l each ofwhich is locked against turning, for eiTecting said attachment, said-bolt having a hole therein, said piston adjacent the bolt having a mating holefand a pin -engaging in the holes for preventing 4the bolt from turnmg.

4. A bi-metallic piston comprising a head of light alloy, wrist-pin bosses integral with the head, a tubular steel skirt provided peripherally with depressions forming substantially flat annular portions, vsaid bosses having annular recesses about the outer ends thereof confronting the inside of the skirt, said flat annular portions seating in said recesses, and inwardly-extending anges on` the iiat annular portions which are co-axial with the Wrist-pin bosses.

5. A bi-metallic piston comprising a head, bosses integral With the head, a tubular skirt, a substantially ilat annular po-rtion on said tubular skirt, said bosses each terminating. at their outer ends in peripheral recesses and said annular skirt portion being received in a recess, and means integral with the at annular skirt portion and extending inwardly of the bosses for securing the skirt to the bosses.

6, A bi-metallic piston comprising a head, a body part integral With the head, Va tubular skirt surrounding said body part, a substantially flat annular portion on the skirt, said body part having a peripheral recess and said annular portion being received in the recess, and means connecting said annular portion to said body part, said means extending inwardly of said body part in the Vicinity of the recess thereinand the eX- ternal surface of said annular portion being wholly out of contact with said body part.

7. A loi-metallic piston comprising a head and body of light metal or alloy, said body having co-axial openings for a wrist-pin formed in it, a tubular skirt of steel or cast iron surrounding said body, said skirt being provided peripherally with depressions forming substantially at annular portions, said body having annular recesses to receive said annular portions, the centers of said annular recesses lying in a longitudinal plane with the axis of said openings, and means uniting said annular portions to said body, the external surfaces of said annular portions being wholly out of contact with said body.

8. A piston, as claimed in claim '7, characterized by each of said means being a tubular flange of said annular portion.

9. A piston, as claimed in claim 7, characterized by each of said means being a frustumshaped tubular ilange of said annular portion.

10. A piston, as claimed in claim 7, characterized by each of said means being a tubular ilange of said annular portion, each of said tubular lian-ges having an outwardly-flared edge Within said body.

11. A bimetallic piston comprising a head, a body part integral With the head, a tubular skirt surrounding the body part, the skirt having a substantially flat annular portion merging, at the ends of a diameter, directly into the tubular portion of the skirt and said annular portion also being connected with the tubular portion ofthe skirt, at the ends of a diameter perpendicular to the first-mentioned diameter, by oppositely-sloping portions, and means connecting said annular portion to the body part.

ALPHEUS FLOWER. 

